Inverse bremsstrahlung absorption in laser-fusion plasma

Abstract

Inverse bremsstrahlung absorption (IBA) is the most efficient absorption mechanism in laser-fusion plasma. IBA is the process in which an electron absorbs a photon while colliding with an ion or with another electron. IBA of laser energy in homogeneous and unmagnetized plasma has been studied using the Fokker–Planck equation. The isotropic function is considered as a q-nonextensive electrons distribution function. By considering a circular-polarized laser, kinetic theory and spherical coordinates, the first anisotropic function is calculated. A pulsed laser is considered, and the effect of the physical parameters such as temperature and q (q is a parameter quantifying the degree of nonextensivity) has been studied on the absorption value. Later, the results of continuous laser and pulsed laser have been compared. The calculations of IBA performed for a variety of q. According to our calculations, the IBA value in neighboring of the critical density layer for continuous laser is higher than pulsed laser. The final results show the IBA value increases with increase in $q$ parameter and oppositely it decreases with temperature increasing.